Glutathione

Glutathione (GSH) is a tripeptide composed of γ-glutamic acid, cysteine, and glycine. It is the most abundant intracellular antioxidant in mammalian cells and plays central roles in redox balance, detoxification, immune function, and the recycling of other antioxidants such as vitamins C and E. Unlike most peptides discussed in research contexts, glutathione is synthesized naturally by virtually every cell in the body, but endogenous levels decline measurably with age, chronic illness, and oxidative stress. As a research compound, glutathione is studied across several areas: intravenous (IV) administration for early Parkinson's disease; nebulized or IV use in pulmonary and immune conditions; skin-lightening effects via IV (widely practiced in parts of Asia, with growing clinical literature); and oral supplementation to raise systemic stores. The route of administration is critical because glutathione is poorly absorbed intact through the gastrointestinal tract under standard oral dosing — the peptide bond is cleaved by gut enzymes before systemic absorption. Liposomal oral formulations and other delivery strategies have been developed specifically to address this limitation, with clinical trials showing meaningful elevations in blood and tissue GSH levels. Glutathione is not an approved drug for most indications studied in research settings. IV glutathione for Parkinson's, skin lightening, and general antioxidant supplementation are all outside approved labeling in most regulatory jurisdictions. This entry summarizes the published evidence and community practice for reference only. It is not medical advice and does not endorse human self-administration.